\documentclass{article}
\usepackage{amssymb,amsmath,amscd,concmath}
\pagestyle{empty}
\begin{document}
\begin{equation*}\mathbf{k}\mathbf{i} = (\mathbf{i}\mathbf{j})\mathbf{i} = -(\mathbf{j}\mathbf{i})\mathbf{i} = \mathbf{j}\end{equation*}
\end{document}
